Reduced levels of free and total testosterone have been associated with type 2 diabetes (T2DM), central adiposity, dyslipidaemia, and hyperinsulinaemia in various studies [24–26, 57–61], usually in combination with reduced LHRH and LH levels however, the observation of low testosterone levels remains relatively rare in men with type 1 diabetes suggesting that hyperglycaemia is not a direct cause. This evidence concerns the gene PLOD1 and type 2 diabetes mellitus.